If you have to park your car in a huge lot, a side street or somewhere that might be hard to locate later, you can use Google Maps' "Starred Items" to pin it down for later locating.
Commenter OCEntertainment gives us this tip, which he discovered and tested first-hand while visiting a friend on a large university campus. Not entirely sure where he'd parked, or where he was headed, he pulled out his phone, turned on GPS, got a fix on his location, then tapped and held right next to that blue arrow. When Google found an approximate location pointer, he "starred" that spot for easy look-up later.
And it was a good thing, too. While hunting for her dorm, I got turned around a couple of times, but being able to refer back to the map helped considerably. It occurs to me that I could use this at theme parks, or, as I did when I left, to mark the location of my friend's dorm on a college campus where addresses aren't quite specific enough, and you can't drive a car up to the front door.
It might not be quite so feasible if you're located far from anything Google Maps recognises — or, obviously, without a data connection — but works just fine if you're parking somewhere that Maps can pin down your spot. Smart move!